History of the S&P 500: From 1923 to Today
A weekly list of 233 companies became the world's benchmark index. The timeline, the crashes, and what a century actually returned.
Before the 500: 1923–1957
The S&P 500 is younger than it looks. Its parent, Standard Statistics Company, published its first stock market index in 1923 — 233 companies, updated weekly. In 1926 came a daily 90-stock composite (50 industrials, 20 railroads, 20 utilities), and in 1941 Standard Statistics merged with Poor's Publishing to form Standard & Poor's. That 90-stock daily series is why long-run S&P 500 charts — including ours — extend back to 1928, decades before the modern index existed: the early history is the backfilled record of the predecessor composite.
March 4, 1957: the modern index
On March 4, 1957 the composite expanded to 500 companies — 425 industrials, 25 railroads, 50 utilities — and became the S&P 500. Its level was benchmarked to a 1941–1943 base period set equal to 10, and it was computed by machine on electronic punch cards, which made it the first major stock index generated by computer rather than by hand. Coverage, not tradition, was the point: where the 30-stock Dow samples blue chips and weights them by share price, the 500 weights companies by market value and was designed to represent the broad U.S. large-cap market.
The milestones that built it
| Year | What happened |
|---|---|
| 1923 | Standard Statistics Company publishes its first stock index, tracking 233 U.S. companies weekly. |
| 1926 | A daily 90-stock composite begins — 50 industrials, 20 rails, 20 utilities. This is the series later backfilled into today's charts. |
| 1941 | Standard Statistics merges with Poor's Publishing to form Standard & Poor's. |
| Mar 4, 1957 | The S&P 500 launches: 425 industrials, 25 rails, 50 utilities, computed by machine against a 1941–43 base of 10 — the first major computer-generated index. |
| Aug 31, 1976 | Vanguard opens the first retail index fund tracking the 500. The same year the fixed industry quotas are revised. |
| Apr 21, 1982 | The Chicago Mercantile Exchange lists S&P 500 futures — the index becomes a tradable instrument. |
| 1988 | Fixed sector quotas are abandoned entirely; weights float with the economy. |
| Jan 22, 1993 | SPY lists on the AMEX — the first U.S.-listed ETF, wrapping the index itself. |
| 2005 | The index moves to float-adjusted market-cap weighting, counting only tradable shares. |
| Today | Seven mega-cap technology companies — the Magnificent 7 — carry about 32% of the index's weight, a concentration not seen since the early 1970s. |
Two of those dates matter more than the rest. The 1976 Vanguard fund turned the index from a yardstick into something an ordinary saver could own; the 1993 launch of SPY did the same for intraday trading and made the S&P 500 the underlying of the largest ETF in the world. The index stopped describing the market and started being the market.
What a century of the index looks like
The backfilled series opens in 1928 at 17.57 points. As of 2026-07-10 the index stands at 7,575 — a 431× price multiple, compounding at +6.4% per year before dividends. With dividends reinvested, the 99 calendar years since 1928 averaged +11.9% arithmetically: 73 positive years against 26 negative ones. The best calendar year on record is 1954 (+52.6%); the worst is 1931 (−43.8%). The year-by-year ledger and the entry-year × exit-year matrix hold the full record.
The crashes along the way
The century was not a straight line. Our register counts 73 drawdowns since 1928, 12 of them full bear markets. The five deepest:
| Period | Decline | Days to trough | Days to recover | Cause |
|---|---|---|---|---|
| 1929: Sep 16 - Jun 1, 1932 | −86.2% | 989 | 9137 | — |
| 2007: Oct 9 - Mar 9, 2009 | −56.8% | 517 | 1997 | Global financial crisis |
| 2000: Mar 24 - Oct 9, 2002 | −49.1% | 929 | 2623 | Dotcom bust |
| 1973: Jan 11 - Oct 3, 1974 | −48.2% | 630 | 2744 | — |
| 1968: Nov 29 - May 26, 1970 | −36.1% | 543 | 1193 | — |
The deepest — −86.2% across 1929–1932 — took a generation to repair. The interactive drawdown register names every fall; the crash history tells them as stories.
The index today
Structurally, today's S&P 500 would be unrecognizable to 1957: railroads have vanished from the top table, and information technology dominates the sector weights. Concentration is back at historic extremes — the Magnificent 7 alone are about 32% of the index. Valuation sits near the top of the historical range too: the Shiller CAPE reads 42.2× against a long-run mean of 17.5×, the 99th percentile of readings since 1871 — the live chart is here, and the decade-by-decade Top 10 rosters show how completely the cast has turned over beneath the index's continuity.
FAQ
When was the S&P 500 created?
The modern 500-stock index launched on March 4, 1957. Its direct ancestors are older: Standard Statistics' first index (1923) and the daily 90-stock composite (1926), whose record is backfilled into long-run S&P 500 charts.
Why does S&P 500 data go back to 1928 if the index started in 1957?
Long-run series splice the S&P 90 predecessor composite onto the modern index. Our dataset opens in 1928 at 17.57 points.
What is the difference between the S&P 500 and SPY?
The S&P 500 is the index — a calculation, not a product. SPY (launched January 22, 1993, the first U.S.-listed ETF) is a fund that owns the 500 stocks and tracks the index; buying SPY, VOO or IVV is how investors own the index in practice.
What was the S&P 500's worst crash?
The 1929–1932 collapse, −86.2% peak to trough — the deepest of the 12 bear markets on record.
How much has the S&P 500 returned over its history?
Price-only, +6.4% compounded per year from 1928 to 2026; with dividends reinvested the arithmetic average of calendar years is +11.9%.
Numbers computed from /api/sp500/century.json, /api/sp500/drawdowns.json and /api/sp500/pe.json, refreshed each trading day. Institutional dates from S&P Dow Jones Indices and Library of Congress records.